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Efavirenz helps control your HIV infection, thereby improving your quality of life. It is used in combination with other anti-HIV medications. It helps to decrease the amount of HIV in your body so your immune system can work better. It also lowers your risk of getting HIV disease complications (such as new infections, cancer). Efavirenz belongs to a class of drugs known as non-nucleoside reverse transcriptase inhibitors (NNRTIs). Efavirenz is not a cure for HIV infection and it does not prevent the spread of HIV to others through sexual contact or blood contamination (such as sharing used needles).

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

Read the Patient Information Leaflet if available from your pharmacist before you start taking efavirenz and each time you get a refill. If you have any questions regarding the information, consult your doctor or pharmacist. Take this medication by mouth on an empty stomach, without food, usually once daily at bedtime or as directed by your doctor. Swallow this medication with water. Taking efavirenz with food increases the blood level of this medication, which may increase your risk of certain side effects. See Side Effects section. The dosage is based on your medical condition and response to treatment. In children, the dosage is also based on weight. If you are taking HIV medications for the first time, you may experience symptoms of an old infection as your immune system begins to work better. Tell your doctor immediately if you notice any trouble breathing, fever, new cough, vision problems, headaches, or skin problems. It is very important to continue taking this medication (and other HIV medications) exactly as prescribed by your doctor. Do not skip any doses. Do not increase your dose, take this drug more often than prescribed, or stop taking it (or other HIV medicines) even for a short time unless directed to do so by your doctor. Skipping or changing your dose without approval from your doctor may cause the amount of virus to increase, make the infection more difficult to treat (resistant), or worsen side effects. This medication works best when the amount of drug in your body is kept at a constant level. Therefore, take this drug at evenly spaced intervals. To help you remember, take it at the same time each day. Tell your doctor if your condition does not improve or if it worsens.

The effects of some drugs can change if you take other drugs or herbal products at the same time. This can increase your risk for serious side effects or may cause your medications not to work correctly. These drug interactions are possible, but do not always occur. Your doctor or pharmacist can often prevent or manage interactions by changing how you use your medications or by close monitoring. To help your doctor and pharmacist give you the best care, be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products) before starting treatment with this product. While using this product, do not start, stop, or change the dosage of any other medicines you are using without your doctor's approval. Do not take this medication with other products that contain efavirenz. Other medications can affect the removal of efavirenz from your body, which may affect how efavirenz works. Examples include some drugs used to treat seizures (such as carbamazepine, phenobarbital, phenytoin), rifamycins (such as rifampin), St. John's wort, among others. Efavirenz can speed up or slow down the removal of many other medications from your body, which may affect how they work. Examples of affected drugs include some drugs for anxiety/sleep (such as alprazolam, midazolam, triazolam), azole antifungals (such as itraconazole, ketoconazole, voriconazole), calcium channel blockers (such as diltiazem, verapamil), cisapride, ergot drugs (such as ergotamine), macrolide antibiotics (such as clarithromycin), methadone, pimozide, rifabutin, sertraline, some cholesterol-lowering statins (such as atorvastatin, pravastatin, simvastatin), warfarin, among others. Some other drugs to treat HIV infection (including protease inhibitors such as saquinavir, lopinavir/ritonavir) may also interact with efavirenz. Your doctor will adjust your medications and monitor your treatment to reduce the risk of side effects. This medication may decrease the effectiveness of hormonal birth control products (such as pills, patch, ring). This effect can result in pregnancy. Ask your doctor or pharmacist for details. Discuss whether you should use additional reliable birth control methods while taking this medication. Tell your doctor or pharmacist if you are taking other products that cause drowsiness including alcohol, antihistamines (such as cetirizine, diphenhydramine), drugs for sleep or anxiety (such as diazepam, zolpidem), muscle relaxants, and narcotic pain relievers (such as codeine). Check the labels on all your medicines (such as allergy or cough-and-cold products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those products safely. This medication may interfere with certain laboratory tests (including urine cannabinoid tests), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug. This document does not contain all possible drug interactions. Keep a list of all the products you use. Share this list with your doctor and pharmacist to lessen your risk for serious medication problems.

Your condition can cause complications in a medical emergency. For enrollment information call MedicAlert at 1-800-854-1166 (US) or 1-800-668-1507 (Canada).

Do not share this medication with others. Laboratory and/or medical tests (such as liver tests, viral load, T-cell counts, cholesterol and triglyceride levels) should be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details. Keep all medical and laboratory appointments.

If overdose is suspected, contact a poison control center or emergency room immediately. US residents can call the US National Poison Hotline at 1-800-222-1222. Canada residents can call a provincial poison control center.

Before taking efavirenz, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. Before using this medication, tell your doctor or pharmacist your medical history, especially of: mental/mood conditions (such as depression, thoughts of suicide, psychosis), liver problems (such as hepatitis B or C, cirrhosis), drug/substance/alcohol abuse, seizures, high cholesterol/triglyceride levels. This drug may make you dizzy or drowsy or cause trouble concentrating. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Avoid alcoholic beverages. A rash may be more common and serious in children taking efavirenz. Report any rash immediately. The doctor may prescribe an antihistamine for your child to take before efavirenz is started. Consult the doctor for more information. To decrease your risk of spreading HIV disease to others, always use an effective barrier method (latex or polyurethane condoms/dental dams) during all sexual activity. Consult your doctor or pharmacist for more details. This medication is not recommended for use during pregnancy. It may harm an unborn baby, especially if taken during the first 3 months of pregnancy. Women of childbearing age should have a pregnancy test before starting efavirenz. It is important to prevent pregnancy while taking this medication and for 3 months after treatment. Consult your doctor about using at least 2 reliable forms of birth control (such as condoms with birth control pills) during treatment and for 3 months after the end of treatment. Efavirenz decreases the effectiveness of hormonal birth control products, so you must always use a barrier protection with these products. If you become pregnant or think you may be pregnant, tell your doctor immediately. Discuss the risks and benefits of HIV treatment and alternatives to efavirenz during pregnancy to decrease the risk of HIV transmission to the baby. It is not known if efavirenz passes into breast milk. Because breast milk can transmit HIV, do not breast-feed.

Store at room temperature at 77 degrees F (25 degrees C) away from light and moisture. Brief storage between 59-86 degrees F (15-30 degrees C) is permitted. Do not store in the bathroom. Keep all medicines away from children and pets. Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

See also How to Use section. Dizziness, trouble sleeping, drowsiness, unusual dreams, and trouble concentrating may frequently occur. These side effects may begin 1-2 days after starting this medication and usually go away in 2-4 weeks. They are also reduced by taking efavirenz on an empty stomach at bedtime. Avoid alcohol and street drugs while taking efavirenz. They may worsen these side effects. Tiredness, headache, nausea, vomiting, and diarrhea may also occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Infrequently, serious psychiatric symptoms may occur during efavirenz treatment, although it is unclear if they are caused by efavirenz. These effects may be seen especially in people who have mental/mood conditions. Tell your doctor immediately if any of these unlikely but serious side effects occur: mental/mood changes (such as depression, rare thoughts of suicide, nervousness, angry behavior, hallucinations). Tell your doctor immediately if any of these rare but serious side effects occur: signs of liver problems (such as persistent nausea/vomiting, stomach/abdominal pain, severe tiredness, yellowing eyes/skin, dark urine). Changes in body fat may occur while you are taking this medication (such as increased fat in the upper back and stomach areas, decreased fat in the arms and legs). The cause and long-term effects of these changes are unknown. Discuss the risks and benefits of treatment with your doctor, as well as the possible use of exercise to reduce this side effect. Efavirenz can commonly cause a rash that is usually not serious. A rash may occur in the first 2 weeks after starting treatment and if it is not serious, it will usually resolve in 4 weeks. However, you may not be able to tell it apart from a rare rash that could be a sign of a severe reaction. Therefore, seek immediate medical attention if you develop any rash. A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include: rash, blisters, peeling skin, fever, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional. Efavirenz may also be used with other medications to prevent HIV infection after contact with the virus.